Our long-term objective is to successfully intervene in the progression of primary open-angle glaucoma (POAG), one of the leading causes of blindness in the world. Early detection of POAG and treatment has proven to be one of the most successful ways to stop blindness from ensuing. The causes of POAG are numerous involving both environmental and genetic determinants. Several forms of POAG have been shown to result from a specific gene defect. Our lab is pursuing the identification of the GLC1C and GLC1F POAG genes. A small isolated pocket of Northern Greece, Epirus, may hold an important key to identifying the POAG GLC1C gene. A large family from Epirus with over 12 individuals with POAG carries the GLC1C gene. We propose that GLC1C is the major POAG gene in this region based on the isolation of the population with little or no interaction with outside populations over the last two centuries. If so, haplotype analysis of Epirian families and individuals with POAG, will identify a founder chromosome and should dramatically reduce the size of the GLC1C region to be searched for the POAG gene. A similar strategy will be used to analyze US and Australian POAG families that show positive evidence for linkage to GLC1C or GLC1F. Identification of a GLC1C and a GLC1F founder haplotype could be used as a screening tool for detecting POAG individuals carrying either the GLC1C or GLC1F gene. While screening tools are important, identification of the GLC1C and GLC1F genes is our ultimate goal. Mutational analysis of candidate genes contained within the GLC1C and GLC1F regions refined by haplotype analysis will be a major goal of this proposal, The last aim of this proposal will be to analyze our Greek and US POAG families and random POAG individuals for mutations in the known POAG genes, MYOC and OPTN. Identification and characterization of the GLC1C and GLC1F POAG genes will point the way to new avenues for research for treatment and/or prevention of blindness resulting from POAG.